Method for performing a logical channel prioritization and communication device thereof

ABSTRACT

There is provided a method for performing a logical channel prioritization. The method may comprise: receiving an uplink (UL) grant; identifying a set of logical channels whose data are to be transmitted using the uplink grant; and performing a logical channel prioritization (LCP) based on the identified set of logical channels.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to wireless communication, and morespecifically, to a method for performing a logical channelprioritization and a communication device thereof.

2. Related Art

3rd generation partnership project (3GPP) long term evolution (LTE) isan improved version of a universal mobile telecommunication system(UMTS) and is introduced as the 3GPP release 8. The 3GPP LTE usesorthogonal frequency division multiple access (OFDMA) in a downlink, anduses single carrier-frequency division multiple access (SC-FDMA) in anuplink. The 3GPP LTE employs multiple input multiple output (MIMO)having up to four antennas. In recent years, there is an ongoingdiscussion on 3GPP LTE-advanced (LTE-A) that is an evolution of the 3GPPLTE.

Examples of techniques employed in the 3GPP LTE-A include carrieraggregation.

The carrier aggregation uses a plurality of component carriers. Thecomponent carrier is defined with a center frequency and a bandwidth.One downlink component carrier or a pair of an uplink component carrierand a downlink component carrier is mapped to one cell. When a userequipment receives a service by using a plurality of downlink componentcarriers, it can be said that the user equipment receives the servicefrom a plurality of serving cells. That is, the plurality of servingcells provides a user equipment with various services.

In recent, there is a discussion for adopting small cells.

SUMMARY OF THE INVENTION

In the related art as above explained, due to adoption of the smallcells, it will be possible for the UE to have dual connectivities toboth a conventional cell and a small cell. However, there is yet noconcept and technique to realize dual connectivities.

Therefore, an object of the present invention is to provide solutions torealize dual connectivities.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described herein,there is provided a method for performing a logical channelprioritization. The method may comprise: receiving an uplink (UL) grant;identifying a set of logical channels whose data are to be transmittedusing the uplink grant; and performing a logical channel prioritization(LCP) based on the identified set of logical channels.

The performing the LCP is further based on a control data to betransmitted using the uplink grant.

The method may further comprise: connecting with a first base stationvia a first MAC entity; and connecting with a second base station via asecond MAC entity.

The performing of the LCP may include: if the first MAC entity receivesthe uplink grant, generating, by the first MAC entity, data unit basedon the LCP; and transmitting, by the first MAC entity, the generateddata unit to the first base station. Here, the generated data unit mayinclude data from the identified set of logical channels, except for adata from logical channels related to the second MAC entity and exceptfor a control data related to the second MAC entity.

Alternatively, the performing of the LCP may include: if the second MACentity receives the uplink grant, generating, by the second MAC entity,data unit based on the LCP; and transmitting, by the second MAC entity,the generated data unit to the second base station. Here, the generateddata unit may include: data from the identified set of logical channels,except for data from logical channels related to the first MAC entityand except for a control data related to the first MAC entity.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described herein,there is also provided a communication device configured for performinga logical channel prioritization. The communication device may comprise:a radio frequency (RF) unit; and a processor connected with the RF unitthereby to control to: receive an uplink (UL) grant, identify a set oflogical channels whose data are to be transmitted using the uplink grantand perform a logical channel prioritization (LCP) based on theidentified set of logical channels.

According to the present specification, the above-explained problem maybe solved. In other words, one embodiment of the present specificationsolves a problem that the UE transmits the second radio bearer's dataunrelated to the first radio bearer via which the UL grant is received.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless communication system to which the presentinvention is applied.

FIG. 2 is a diagram showing a radio protocol architecture for a userplane.

FIG. 3 is a diagram showing a radio protocol architecture for a controlplane.

FIG. 4 shows an example of a wideband system using carrier aggregationfor 3GPP LTE-A.

FIG. 5 shows an example of a structure of DL layer 2 when carrieraggregation is used.

FIG. 6 shows an example of a structure of UL layer 2 when carrieraggregation is used.

FIG. 7 an example of a logical channel prioritization (LCP) procedure.

FIG. 8 shows one exemplary concept of coexistence of a macro cell andsmall cells.

FIG. 9 shows one example of a first scenario of small cell deployment.

FIG. 10 a shows one example of a second scenario of small celldeployment.

FIG. 10 b shows another example of the second scenario of small celldeployment.

FIG. 11 shows one example of a third scenario of small cell deployment.

FIG. 12 shows a concept of dual connectivities

FIG. 13 shows radio protocols of eNodeBs for supporting dualconnectivities.

FIG. 14 shows radio protocols of UE for supporting dual connectivities.

FIG. 15 shows one exemplary method according to one embodiment of thepresent disclosure.

FIG. 16 shows one exemplary method according to another embodiment ofthe present disclosure.

FIG. 17 is a block diagram showing a wireless communication system toimplement an embodiment of the present invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. It will also be apparent to those skilled in the art thatvarious modifications and variations can be made in the presentinvention without departing from the spirit or scope of the invention.Thus, it is intended that the present invention cover modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

Description will now be given in detail of a drain device and arefrigerator having the same according to an embodiment, with referenceto the accompanying drawings.

The present invention will be described on the basis of a universalmobile telecommunication system (UMTS) and an evolved packet core (EPC).However, the present invention is not limited to such communicationsystems, and it may be also applicable to all kinds of communicationsystems and methods to which the technical spirit of the presentinvention is applied.

It should be noted that technological terms used herein are merely usedto describe a specific embodiment, but not to limit the presentinvention. Also, unless particularly defined otherwise, technologicalterms used herein should be construed as a meaning that is generallyunderstood by those having ordinary skill in the art to which theinvention pertains, and should not be construed too broadly or toonarrowly. Furthermore, if technological terms used herein are wrongterms unable to correctly express the spirit of the invention, then theyshould be replaced by technological terms that are properly understoodby those skilled in the art. In addition, general terms used in thisinvention should be construed based on the definition of dictionary, orthe context, and should not be construed too broadly or too narrowly.

Incidentally, unless clearly used otherwise, expressions in the singularnumber include a plural meaning. In this application, the terms“comprising” and “including” should not be construed to necessarilyinclude all of the elements or steps disclosed herein, and should beconstrued not to include some of the elements or steps thereof, orshould be construed to further include additional elements or steps.

The terms used herein including an ordinal number such as first, second,etc. can be used to describe various elements, but the elements shouldnot be limited by those terms. The terms are used merely to distinguishan element from the other element. For example, a first element may benamed to a second element, and similarly, a second element may be namedto a first element.

In case where an element is “connected” or “linked” to the otherelement, it may be directly connected or linked to the other element,but another element may be existed there between. On the contrary, incase where an element is “directly connected” or “directly linked” toanother element, it should be understood that any other element is notexisted there between.

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings, and thesame or similar elements are designated with the same numeral referencesregardless of the numerals in the drawings and their redundantdescription will be omitted. In describing the present invention,moreover, the detailed description will be omitted when a specificdescription for publicly known technologies to which the inventionpertains is judged to obscure the gist of the present invention. Also,it should be noted that the accompanying drawings are merely illustratedto easily explain the spirit of the invention, and therefore, theyshould not be construed to limit the spirit of the invention by theaccompanying drawings. The spirit of the invention should be construedas being extended even to all changes, equivalents, and substitutesother than the accompanying drawings.

There is an exemplary UE (User Equipment) in accompanying drawings,however the UE may be referred to as terms such as a terminal, a mobileequipment (ME), a mobile station (MS), a user terminal (UT), asubscriber station (SS), a wireless device (WD), a handheld device (HD),an access terminal (AT), and etc. And, the UE may be implemented as aportable device such as a notebook, a mobile phone, a PDA, a smartphone, a multimedia device, etc., or as an unportable device such as aPC or a vehicle-mounted device.

FIG. 1 shows a wireless communication system to which the presentinvention is applied.

The wireless communication system may also be referred to as anevolved-UMTS terrestrial radio access network (E-UTRAN) or a long termevolution (LTE)/LTE-A system.

The E-UTRAN includes at least one base station (BS) 20 which provides acontrol plane and a user plane to a user equipment (UE) 10. The UE 10may be fixed or mobile, and may be referred to as another terminology,such as a mobile station (MS), a user terminal (UT), a subscriberstation (SS), a mobile terminal (MT), a wireless device, etc. The BS 20is generally a fixed station that communicates with the UE 10 and may bereferred to as another terminology, such as an evolved node-B (eNodeB),a base transceiver system (BTS), an access point, etc.

The BSs 20 are interconnected by means of an X2 interface. The BSs 20are also connected by means of an S1 interface to an evolved packet core(EPC) 30, more specifically, to a mobility management entity (MME)through S1-MME and to a serving gateway (S-GW) through S1-U.

The EPC 30 includes an MME, an S-GW, and a packet data network-gateway(P-GW). The MME has access information of the UE or capabilityinformation of the UE, and such information is generally used formobility management of the UE. The S-GW is a gateway having an E-UTRANas an end point. The P-GW is a gateway having a PDN as an end point.

Layers of a radio interface protocol between the UE and the network canbe classified into a first layer (L1), a second layer (L2), and a thirdlayer (L3) based on the lower three layers of the open systeminterconnection (OSI) model that is well-known in the communicationsystem. Among them, a physical (PHY) layer belonging to the first layerprovides an information transfer service by using a physical channel,and a radio resource control (RRC) layer belonging to the third layerserves to control a radio resource between the UE and the network. Forthis, the RRC layer exchanges an RRC message between the UE and the BS.

FIG. 2 is a diagram showing a radio protocol architecture for a userplane. FIG. 3 is a diagram showing a radio protocol architecture for acontrol plane.

The user plane is a protocol stack for user data transmission. Thecontrol plane is a protocol stack for control signal transmission.

Referring to FIGS. 2 and 3, a PHY layer provides an upper layer with aninformation transfer service through a physical channel. The PHY layeris connected to a medium access control (MAC) layer which is an upperlayer of the PHY layer through a transport channel. Data is transferredbetween the MAC layer and the PHY layer through the transport channel.The transport channel is classified according to how and with whatcharacteristics data is transferred through a radio interface.

Between different PHY layers, i.e., a PHY layer of a transmitter and aPHY layer of a receiver, data is transferred through the physicalchannel. The physical channel may be modulated using an orthogonalfrequency division multiplexing (OFDM) scheme, and may utilize time andfrequency as a radio resource.

Functions of the MAC layer include mapping between a logical channel anda transport channel and multiplexing/de-multiplexing on a transportblock provided to a physical channel over a transport channel of a MACservice data unit (SDU) belonging to the logical channel. The MAC layerprovides a service to a radio link control (RLC) layer through thelogical channel.

Functions of the RLC layer include RLC SDU concatenation, segmentation,and reassembly. To ensure a variety of quality of service (QoS) requiredby a radio bearer (RB), the RLC layer provides three operation modes,i.e., a transparent mode (TM), an unacknowledged mode (UM), and anacknowledged mode (AM). The AM RLC provides error correction by using anautomatic repeat request (ARQ).

Functions of a packet data convergence protocol (PDCP) layer in the userplane include user data delivery, header compression, and ciphering.Functions of a PDCP layer in the control plane include control-planedata delivery and ciphering/integrity protection.

A radio resource control (RRC) layer is defined only in the controlplane. The RRC layer serves to control the logical channel, thetransport channel, and the physical channel in association withconfiguration, reconfiguration and release of radio bearers (RBs). An RBis a logical path provided by the first layer (i.e., the PHY layer) andthe second layer (i.e., the MAC layer, the RLC layer, and the PDCPlayer) for data delivery between the UE and the network.

The setup of the RB implies a process for specifying a radio protocollayer and channel properties to provide a particular service and fordetermining respective detailed parameters and operations. The RB can beclassified into two types, i.e., a signaling RB (SRB) and a data RB(DRB). The SRB is used as a path for transmitting an RRC message in thecontrol plane. The DRB is used as a path for transmitting user data inthe user plane.

When an RRC connection is established between an RRC layer of the UE andan RRC layer of the network, the UE is in an RRC connected state (alsomay be referred as an RRC connected mode), and otherwise the UE is in anRRC idle state (also may be referred as an RRC idle mode).

Data is transmitted from the network to the UE through a downlinktransport channel. Examples of the downlink transport channel include abroadcast channel (BCH) for transmitting system information and adownlink-shared channel (SCH) for transmitting user traffic or controlmessages. The user traffic of downlink multicast or broadcast servicesor the control messages can be transmitted on the downlink-SCH or anadditional downlink multicast channel (MCH). Data is transmitted fromthe UE to the network through an uplink transport channel. Examples ofthe uplink transport channel include a random access channel (RACH) fortransmitting an initial control message and an uplink SCH fortransmitting user traffic or control messages.

Examples of logical channels belonging to a higher channel of thetransport channel and mapped onto the transport channels include abroadcast channel (BCCH), a paging control channel (PCCH), a commoncontrol channel (CCCH), a multicast control channel (MCCH), a multicasttraffic channel (MTCH), etc.

The physical channel includes several OFDM symbols in a time domain andseveral subcarriers in a frequency domain. One subframe includes aplurality of OFDM symbols in the time domain. A resource block is aresource allocation unit, and includes a plurality of OFDM symbols and aplurality of subcarriers. Further, each subframe may use particularsubcarriers of particular OFDM symbols (e.g., a first OFDM symbol) of acorresponding subframe for a physical downlink control channel (PDCCH),i.e., an L1/L2 control channel. A transmission time interval (TTI) is aunit time of subframe transmission.

Hereinafter, an RRC state of a UE and an RRC connection mechanism willbe described.

The RRC state indicates whether an RRC layer of the UE is logicallyconnected to an RRC layer of an E-UTRAN. If the two layers are connectedto each other, it is called an RRC connected state, and if the twolayers are not connected to each other, it is called an RRC idle state.When in the RRC connected state, the UE has an RRC connection and thusthe E-UTRAN can recognize a presence of the UE in a cell unit.Accordingly, the UE can be effectively controlled. On the other hand,when in the RRC idle state, the UE cannot be recognized by the E-UTRAN,and is managed by a core network in a tracking area unit which is a unitof a wider area than a cell. That is, regarding the UE in the RRC idlestate, only a presence or absence of the UE is recognized in a wide areaunit. To get a typical mobile communication service such as voice ordata, a transition to the RRC connected state is necessary.

When a user initially powers on the UE, the UE first searches for aproper cell and thereafter stays in the RRC idle state in the cell. Onlywhen there is a need to establish an RRC connection, the UE staying inthe RRC idle state establishes the RRC connection with the E-UTRANthrough an RRC connection procedure and then transitions to the RRCconnected state. Examples of a case where the UE in the RRC idle stateneeds to establish the RRC connection are various, such as a case whereuplink data transmission is necessary due to telephony attempt of theuser or the like or a case where a response message is transmitted inresponse to a paging message received from the E-UTRAN.

A non-access stratum (NAS) layer belongs to an upper layer of the RRClayer and serves to perform session management, mobility management, orthe like.

Now, a radio link failure will be described.

A UE persistently performs measurement to maintain quality of a radiolink with a serving cell from which the UE receives a service. The UEdetermines whether communication is impossible in a current situationdue to deterioration of the quality of the radio link with the servingcell. If it is determined that the quality of the serving cell is sopoor that communication is almost impossible, the UE determines thecurrent situation as a radio link failure.

If the radio link failure is determined, the UE gives up maintainingcommunication with the current serving cell, selects a new cell througha cell selection (or cell reselection) procedure, and attempts RRCconnection re-establishment to the new cell.

FIG. 4 shows an example of a wideband system using carrier aggregationfor 3GPP LTE-A.

Referring to FIG. 4, each CC has a bandwidth of 20 MHz, which is abandwidth of the 3GPP LTE. Up to 5 CCs may be aggregated, so maximumbandwidth of 100 MHz may be configured.

FIG. 5 shows an example of a structure of DL layer 2 when carrieraggregation is used. FIG. 6 shows an example of a structure of UL layer2 when carrier aggregation is used.

The carrier aggregation may affect a MAC layer of the L2. For example,since the carrier aggregation uses a plurality of CCs, and each hybridautomatic repeat request (HARQ) entity manages each CC, the MAC layer ofthe 3GPP LTE-A using the carrier aggregation shall perform operationsrelated to a plurality of HARQ entities. In addition, each HARQ entityprocesses a transport block independently. Therefore, when the carrieraggregation is used, a plurality of transport blocks may be transmittedor received at the same time through a plurality of CCs.

<Logical Channel Prioritization (LCP)>

Now, a Logical Channel Prioritization (LCP) will be described below. Itmay be referred to 3GPP TS 36.321 V10.5.0.

In order to provide various types of services, at least one RB may beconfigured. A logical channel is allocated to a RB. A plurality oflogical channels corresponding to a plurality of RBs are multiplexed andtransmitted through one transport block (i.e. MAC PDU).

The LCP is a method for multiplexing data of the plurality of RBs (i.e.a plurality of logical channels) into a transport block (i.e. MAC PDU).LCP determines how much amount of given radio resources are allocated toeach of the plurality of RBs.

The LCP procedure is applied when a new transmission is performed. TheRRC controls the scheduling of uplink data by signaling for each logicalchannel: priority where an increasing priority value indicates a lowerpriority level, prioritisedBitRate which sets the prioritized bit rate(PBR), and bucketSizeDuration which sets the bucket size duration (BSD).The priority may have a value between 1 and 8. The priority having avalue of 1 indicates the highest priority, and the priority having avalue of 8 indicates the lowest priority. The PBR indicates a minimumbit rate guaranteed for corresponding RB. That is, a bit rate indicatedby the PBR is always guaranteed.

The UE shall maintain a variable Bj for each logical channel j. Bj shallbe initialized to zero when the related logical channel is established,and incremented by the product PBR×TTI duration for each TTI, where PBRis prioritized bit rate of logical channel j. However, the value of Bjcan never exceed the bucket size and if the value of Bj is larger thanthe bucket size of logical channel j, it shall be set to the bucketsize. The bucket size of a logical channel is equal to PBR×BSD, wherePBR and BSD are configured by upper layers.

The UE shall perform the following LCP procedure when a new transmissionis performed. The UE shall allocate resources to the logical channels inthe following steps.

-   -   Step 1: All the logical channels with Bj>0 are allocated        resources in a decreasing priority order. If the PBR of a radio        bearer is set to “infinity”, the UE shall allocate resources for        all the data that is available for transmission on the radio        bearer before meeting the PBR of the lower priority radio        bearer(s);    -   Step 2: The UE shall decrement Bj by the total size of MAC SDUs        served to logical channel j in Step 1. The value of Bj can be        negative.    -   Step 3: If any resources remain, all the logical channels are        served in a strict decreasing priority order (regardless of the        value of Bj) until either the data for that logical channel or        the UL grant is exhausted, whichever comes first. Logical        channels configured with equal priority should be served        equally.

The UE shall also follow the rules below during the schedulingprocedures above:

-   -   the UE should not segment an RLC SDU (or partially transmitted        SDU or retransmitted RLC PDU) if the whole SDU (or partially        transmitted SDU or retransmitted RLC PDU) fits into the        remaining resources;    -   if the UE segments an RLC SDU from the logical channel, it shall        maximize the size of the segment to fill the grant as much as        possible;    -   the UE should maximize the transmission of data.    -   if the UE is given an UL grant size that is equal to or larger        than 4 bytes while having data available for transmission, the        UE shall not transmit only padding BSR and/or padding (unless        the UL grant size is less than 7 bytes and an AMD PDU segment        needs to be transmitted).

The UE shall not transmit data for a logical channel corresponding to aradio bearer that is suspended.

A priority and/or a PBR of a logical channel of each RB are transmittedfrom a RRC layer of a network to a RRC layer of an UE through a RB setupmessage when the RB is initially configured. The RRC layer of the UEwhich receives the RB setup message configures a RB and sendsinformation on the LCP and the PBR of the logical channel of each RB tothe MAC layer of the UE. The MAC layer that receives the informationdetermines amounts of transmission data of the RB according to the LCPfor each TTI.

FIG. 7 an example of a logical channel prioritization (LCP) procedure.

Referring to FIG. 7, there are three RBs, i.e., an RB1 to which alogical channel of a highest priority P1 is mapped, an RB2 to which alogical channel of a second priority P2 is mapped, and an RB3 to which alogical channel of a lowest priority P3 is mapped. In addition, a PBR ofthe RB1 is a PBR 1, a PBR of the RB2 is a PBR 2, and a PBR or a RB3 is aPBR 3. First, a transmission data amount is determined according to datacorresponding to a PRB in each RB in a descending order of priority oflogical channels mapped to the RB1, the RB2, and the RB3. That is, thetransmission data amount can be determined to the PBR 1 in the RB1, thePBR 2 in the RB2, and the PBR 3 in the RB3. Since there are remainingradio resources even if a transmission data amount corresponding to thePBR in each RB is fully allocated, the remaining radio resources can beallocated to the RB1 having the highest priority.

For the LCP procedure, the UE shall take into account the followingrelative priority in decreasing order:

-   -   MAC control element for C-RNTI or data from UL-CCCH;    -   MAC control element for BSR, with exception of BSR included for        padding;    -   MAC control element for PHR;    -   data from any Logical Channel, except data from UL-CCCH;    -   MAC control element for BSR included for padding.

<Small Cell>

Now, a concept of small cell will be described.

In the 3rd or 4th mobile communication system, an attempt to increase acell capacity is continuously made in order to support a high-capacityservice and a bidirectional service such as multimedia contents,streaming, and the like.

That is, as various large-capacity transmission technologies arerequired with development of communication and spread of multimediatechnology, a method for increase a radio capacity includes a method ofallocating more frequency resources, but there is a limit in allocatingmore frequency resources to a plurality of users with limited frequencyresources.

An approach to use a high-frequency band and decrease a cell radius hasbeen made in order to increase the cell capacity. When a small cell suchas a pico cell or femto cell is adopted, a band higher than a frequencyused in the existing cellular system may be used, and as a result, it ispossible to transfer more information.

FIG. 8 shows one exemplary concept of coexistence of a macro cell andsmall cells.

As shown in FIG. 8, a cell of a conventional BS or eNodeB (200) may becalled as a macro cell over small cells. Each small cell is operated byeach small BS or eNodeB (300). When the conventional BS or eNodeB (200)may operate in use of a frequency F1, each small cell operates in use ofa frequency F1 or F2. Small cells may be grouped in a cluster. It isnoted that actual deployment of small cells are varied depending onoperator's policy.

FIG. 9 shows one example of a first scenario of small cell deployment.

As shown in FIG. 9, the small cells may be deployed in the presence ofan overlaid macro cell. That is, the small cells may be deployed in acoverage of the macro cell. In such deployment, the following may beconsidered.

-   -   Co-channel deployment of the macro cell and small cells    -   Outdoor small cell deployment    -   Small cell cluster is considered    -   The small cells are dense in cluster    -   Details regarding the number/density of small cells per cluster,        backhaul link for coordination among small cells and time        synchronization among small cells may also be considered    -   Both ideal backhaul and non-ideal backhaul may be also        considered for the following interfaces: an interface between        the small cells within the same cluster and an interface between        a cluster of small cells and at least one macro eNodeB.    -   Non-ideal backhaul is assumed for all other interfaces.

Here, the non-ideal backhaul means that there may be a delay up to 60ms.

FIG. 10 a shows one example of a second scenario of small celldeployment.

As shown in FIG. 10 a, the small cells may be deployed outdoor. In suchdeployment, the following may be considered.

-   -   The small cells are deployed in the presence of an overlaid        macro network    -   Separate frequency deployment of the macro cell and small cells    -   Outdoor small cell deployment    -   Small cell cluster is considered    -   The small cells are dense in cluster    -   Details regarding the number/density of small cells per cluster,        backhaul link for coordination among small cells and time        synchronization among small cells may also be considered.    -   Both ideal backhaul and non-ideal backhaul may be also        considered for the following interfaces: an interface between        the small cells within the same cluster and an interface between        a cluster of small cells and at least one macro eNB    -   Non-ideal backhaul is assumed for all other interfaces

FIG. 10 b shows another example of the second scenario of small celldeployment.

As shown in FIG. 10 b, the small cells may be deployed indoor. In suchdeployment, the following may be considered.

-   -   The small cells are deployed in the presence of an overlaid        macro network    -   Separate frequency deployment of the macro cell and small cells    -   Indoor small cell deployment is considered    -   Small cell cluster is considered    -   The small cells are dense in cluster    -   Details regarding the number/density of small cells per cluster,        backhaul link for coordination among small cells and time        synchronization among small cells may also be considered.    -   A sparse scenario can be also considered such as the indoor        hotspot scenario.    -   Both ideal backhaul and non-ideal backhaul may be also        considered for the following interfaces: an interface between        the small cells within the same cluster and an interface between        a cluster of small cells and at least one macro eNB    -   Non-ideal backhaul is assumed for all other interfaces.

FIG. 11 shows one example of a third scenario of small cell deployment.

As shown in FIG. 11, the small cells may be deployed indoor. In suchdeployment, the following may be considered.

-   -   Macro cell coverage is not present    -   Indoor deployment scenario is considered    -   Small cell cluster is considered    -   The small cells are dense in cluster    -   Details regarding the number/density of small cells per cluster,        backhaul link for coordination among small cells and time        synchronization among small cells may also be considered.    -   A sparse scenario can be considered such as the indoor hotspot        scenario.    -   Both ideal backhaul and non-ideal backhaul may be also        considered for the following interfaces: an interface between        the small cells within the same cluster.    -   Non-ideal backhaul is assumed for all other interfaces.

FIG. 12 shows a concept of dual connectivities

As illustrated in FIG. 12, the UE 100 has dual connectivities to bothMacro cell and small cell. Here, the connectivity means the connectionto eNodeB for data transfer. If the UE is served by both one macro celland one small cell, it can be said that the UE has dual connectivities,i.e., one connectivity for the macro cell and another connectivity forthe small cell. If the UE is served by small cells, it can be said thatthe UE has multiple connectivity.

The macro cell is served by CeNodeB (or CeNB) and the small cell orgroup of small cells is served by UeNodeB (or UeNB). The CeNodeB meansControl plane eNodeB that is responsible for managing control planespecific operations, e.g., RRC connection control and mobility, e.g.,transfer of control data on signaling radio bearers (SRBs). The UeNodeBmeans User plane eNodeB that is responsible for managing user planespecific operations, e.g., transfer of data on data radio bearers(DRBs).

The small cell of UeNodeB is responsible for transmitting best effort(BE) type traffic, while the macro cell of the CeNodeB is responsiblefor transmitting other types of traffic such as VoIP, streaming data, orsignaling data.

It is noted that there is X3 interface between CeNodeB and UeNodeB thatis similar to conventional X2 interface between eNodeBs.

FIG. 13 shows radio protocols of eNodeBs for supporting dualconnectivities.

For dual or multiple connectivities, MAC functions of the UE 100 needsto be newly defined because from Layer 2 protocol point of view, RLCfunctions and configurations are bearer-specific while MAC functions andconfigurations are not.

To support dual or multiple connectivities, various protocolarchitectures are studied, and one of potential architectures is shownin FIG. 15. In this architecture, PDCP entity for UeNodeB is located indifferent network nodes, i.e. PDCP in CeNodeB.

As shown in FIG. 13, CeNodeB includes a PHY layer, a MAC layer, an RLClayer, a PDCH layer and an RRC layer while the UeNodeB includes a PHYlayer, a MAC layer and an RLC layer. It is noted that the RRC layer andthe PDCP layer exist only in the CeNodeB. In other words, there is thecommon RRC and PDCP layer and there is a set of RLC, MAC and PHY layersper connectivity. Accordingly, data on SRBs is signaled on CeNodeB anddata on DRBs is signaled on either CeNodeB or UeNodeB according to theDRB configurations. That is, the CeNodeB can deliver data on DRBs inaddition to control data on SRBs, while the UeNodeB can deliver data ononly DRBs.

Here, the followings are considered:

-   -   CeNodeB and UeNodeB can be different nodes.    -   Transfer of data on SRBs is performed on CeNodeB.    -   Transfer of data on DRBs is performed on either CeNodeB or        UeNodeB. Whether path of data on DRBs is on CeNodeB or UeNodeB        can be configured by the eNodeB, MME, or S-GW.    -   There is X3 interface between CeNodeB and UeNodeB that is        similar to conventional X2 interface between eNodeBs.    -   Because RRC connection reconfiguration is managed in the        CeNodeB, the CeNodeB sends information about DRB configurations        to UeNodeB via X3 interface.

FIG. 14 shows radio protocols of UE for supporting dual connectivities.

As shown in FIG. 14, the UeNodeB is responsible for transmitting besteffort (BE) DRB. The CeNodeB is responsible for transmitting SRB andDRB. As above explained, PDCP entity for UeNodeB is located in CeNodeB.

As shown in FIG. 14, on the UE 100 side, there are plural MAC entitiesfor macro cell of CeNodeB and small cells of UeNodeB. In other word, theUE 100 setups each MAC entity for each connectivity. Accordingly, the UE100 includes plural MAC entities for dual or multiple connectivities.Here, although FIG. 16 illustrates two PHY entities for dualconnectivities, only one PHY entity may handle dual connectivities. Forthe connectivity to UeNodeB, the UE 100 may include the PDCP entity, theRLC entity and the MAC entity which handle BE-DRB. For connectivity toCeNodeB, the UE 100 may include plural RLC entities, plural PDCPentities which handle SRB and DRB.

Meanwhile, each of the CeNodeB and the UeNodeB owns a radio resource foritself and include a scheduler for scheduling the radio resource foritself. Here, each scheduler and each connectivity are 1-to-1 mapping.Also, there is a correspondence between connectivity and radio bearer,i.e., there is connectivity-specific radio bearer.

However, in conventional LCP procedure, when an UL grant is available,data from all the radio bearers can be accommodated to the MAC PDUgenerated by the UL grant if possible. It means that even though the ULgrant from a first connectivity is received, data from radio bearerscorresponding to a second connectivity could be accommodated to the MACPDU that will be sent via the first connectivity. So, there is a seriousproblem that the UE transmits the second radio bearer's data unrelatedto the first radio bearer via which the UL grant is received.

Therefore, the present disclosure provides a solution that when the UEreceives the UL grant from a specific eNodeB which is subject to certainconnectivity, the data on radio bearers configured and/or controlinformation for the connectivity is only considered during the LCPprocedure. That is, according to the one embodiment, during LCPprocedure, the UL grant is only applicable to the data on radio bearersconfigured for connectivity for which the UL grant is received.

For the solution, the present disclosure provides one example technique.According to the technique, if the UE having connectivity to a pluralityof cells receives configurations on a plurality of bearers with theplurality of cells, then the UE sets up the plurality of bearers relatedto connectivity to the plurality of cells based on the receivedconfigurations. Afterward, if the UE receives an uplink (UL) grantthrough one connectivity, then the UE performs a logical channelprioritization (LCP) by generating a transport block using data of aradio bearer corresponding to no other than the one connectivity therebyto transmit the transport block based on the uplink grant.

On the other hand, there may be another problem where data on any radiobearer can be delay or discarded when a connectivity relating to theradio bearer is released, deactivated or disconnected.

Therefore, the present disclosure provides another solution that aconnectivity to CeNodeB is considered to a default connectivity, so thatthe UE can associate the radio bearer related to the removed ordeactivated connectivity with the default connectivity.

FIG. 15 shows one exemplary method according to one embodiment of thepresent disclosure.

Referring to FIG. 15, it is illustrated how the LCP procedure isperformed in dual connectivity.

(1) In detail, the UE 100 may receive a configuration on dualconnectivites to CeNodeB (or Macro eNodeB) 200 and UeNodeB (or smalleNodeB) 300. The configuration may indicate that a first connectivity(connectivity 1) is for CeNodeB and a second connected (connectivity 2)is for UeNodeB. Then, the UE 100 may activate (or configure) each MACentity for each connectivity.

(2) And, the UE 100 may receive configuration on a plurality of bearers.The configuration may indicate that a first radio bearer (radiobearer 1) is related to or associated with the first connectivity(connectivity 1) and a second radio bearer (radio bearer 2) is relatedto or associated with the second connectivity (connectivity 2). Then,the UE 100 may associate (or correlate) each MAC entity for eachconnectivity with each radio bearer.

(3) Afterward, the UE 100 receives an UL grant via the firstconnectivity (connectivity 1). Then, the UE 100 identifies a set oflogical channels whose data are to be transmitted using the uplinkgrant.

(4) The UE 100 performs LCP procedure by considering only the data fromthe first radio bearer (radio bearer 1) by using the UL grant. That is,The UE 100 performs LCP procedure based on the identified set of logicalchannels. And the UE 100 generates the PDU by the LCP procedure.

(5) Then, the UE 100 transmits the MAC PDU including only data from thefirst radio bearer (radio bearer 1).

In such a manner, if the UE receives the UL grant from a specific eNodeBwhich is subject to certain connectivity, the one embodiment allows theUE to consider only the data on radio bearers configured and/or controlinformation for the connectivity during the LCP procedure. Therefore,the one embodiment solves the problem that the UE transmits the secondconnectivity's data unrelated to the first connectivity via which the ULgrant is received.

FIG. 16 shows one exemplary method according to another embodiment ofthe present disclosure.

Referring to FIG. 16, it is illustrated how the radio bearer isreconfigured to the connectivity upon removal or deactivation ofconnectivity.

(1) In detail, the UE 100 may receive a configuration on dualconnectivites to CeNodeB (or Macro eNodeB) 200 and UeNodeB (or smalleNodeB) 300. The configuration may indicate that a first connectivity(connectivity 1) is for CeNodeB and a second connected (connectivity 2)is for UeNodeB. Then, the UE 100 may activate (or configure) each MACentity for each connectivity. Here, the configuration on the firstconnectivity (connectivity 1) to CeNodeB is considered as a defaultconfiguration.

(2) And, the UE 100 may receive configuration on a plurality of bearers.The configuration may indicate that a first radio bearer (radiobearer 1) is related to the first connectivity (connectivity 1) and asecond radio bearer (radio bearer 2) is related to the secondconnectivity (connectivity 2). Then, the UE 100 may associate (orcorrelate) each MAC entity for each connectivity with each radio bearer.

(3) Afterward, the UE 100 is requested to remove or deactivate thesecond connectivity (connectivity 2). Or, the UE 100 removes ordeactivates the second connectivity (connectivity 2) by itself accordingto the pre-defined conditions. For example, the UE 100 can be configuredwith connectivity timer for each connectivity. When the UE 100 isconfigured with a new connectivity, the UE starts the connectivity timerfor the new connectivity. If the connectivity timer expires, the UEreleases the connectivity.

(4) The UE 100 sets the second radio bearer (radio bearer 2) to thefirst connectivity (connectivity 1) which is defined as defaultconnectivity.

(5) Then, the UE 100 transmits or removes data both on radio bearer 1and 2 over the first connectivity (connectivity 1).

In such a manner, if at least one connectivity is removed ordeactivated, the UE can associate a radio bearer related to the at leastone removed or deactivated connectivity with another connectivity.Therefore, a delay or discard of data on the radio bearer can beminimized

Hereinafter, other embodiments of the present disclosure will beexplained

<Connectivity Grouping>

For realizing dual connectivity, from UE point of view, one MAC layer isneeded for each eNodeB assuming that there is one connectivity pereNodeB. Because one eNodeB serves one or more cells and cells belongingto the same eNodeB can be handed in one MAC layer, the UE has one MAClayer per connectivity. For dual connectivity, it is assumed that the UEhas at least one connectivity for macro cell(s) and one or moreconnectivity for small cells. For example, the UE is served by one macrocell and two small cells. Those small cells are served by differentUeNodeBs. Then, the UE has 3 connectivity that requires 3 MAC layers.

The connectivity management can be done by CeNodeB, MME or S-GW. Thefollowing is included in the connectivity management.

-   -   Connectivity identifier (Id)

The UE can be configured with connectivity Id for each connectivity bye.g., RRC messages. For example, the UE can be configured withconnectivity Id 0 for CeNodeB, connectivity Id 1 for UeNodeB1, andconnectivity Id 2 for UeNodeB2. The connectivity Id is generally usedfor identification of connectivity between the UE and eNodeB, e.g., whenthe connectivity is added, modified or removed.

-   -   Configuration per connectivity

With connectivity grouping, the common configuration for cells belongingto the same connectivity can be provided to the UE. For example, if theconfigurations are provided with the connectivity Id, the UE applies theconfigurations to the cells belonging to the connectivity indicated bythe connectivity Id.

-   -   Default configuration for connectivity

Configurations for the connectivity for CeNodeB are considered as faultconfiguration. So, if the connectivity is removed, default configurationis applied to the configuration including radio bearer configured forthe removed connectivity. For example, the UE is configured with radiobearers A and B and radio bearer A is configured for CeNodeB(connectivity 1) and radio bearer B is configured for UeNodeB(connectivity 2). If the connectivity 2 is removed, the UE considers theradio bearer B to be configured for connectivity 1.

-   -   Connectivity timer

The UE can be configured with connectivity timer for each connectivity.When the UE is configured with a new connectivity, the UE starts theconnectivity timer for the new connectivity. The UE re-starts theconnectivity timer if the connectivity is modified. If the connectivitytimer expires, the UE releases the connectivity.

-   -   Activation/deactivation of the connectivity

The eNodeB (e.g., CeNodeB) may order the UE to activate or deactivateone, some, all connectivity. When a new connectivity is added to the UE,the UE consider the connectivity to be deactivated. When the eNodeB asksthe UE to activate the connectivity by PDCCH, MAC, RLC, PDCP, RRCsignaling, the UE activates the connectivity. For the activatedconnectivity, the UE can use the data transfer on it. If the eNodeB asksthe UE to deactivate the connectivity, then, the UE deactivates theconnectivity. For the deactivated connectivity, the UE cannot use thedata transfer on it.

<Buffer Status Reporting (BSR)>

Because the scheduler in each eNodeB schedules own radio resources, eachscheduler needs to know the amount of data to schedule.

However, existing BSR mechanism only allows the UE to report the amountof data per logical cannel group (LCG) in one message to one eNodeB. Itimplies that the information about buffer status would need to beexchanged between the eNodeBs that are subject to dual connectivity. So,there would be a delay for the eNodeB to schedule.

Therefore, it is proposed that the BSR procedure is performed perconnectivity. That is, radio bearers configured for a connectivity areconsidered for the BSR procedure for the connectivity. For example, itis assumed that the UE has 2 connectivity (connectivity 1 and 2) and 2sets of radio bearers (set A and B). It is further assumed that set A isused for connectivity 1 and set B is used for connectivity 2. In thiscase, the BSR procedure for connectivity 1 is associated with the dataon radio bearers in set A and the BSR procedure for connectivity 2 isassociated with the data on radio bearers in set B. So,

-   -   If data on radio bears in set A arrives,

The UE triggers the BSR for the connectivity 1. It means that the UEreports the BSR (i.e., BSR MAC CE) to the eNodeB which is subject to theconnectivity 1. Also, if the UE does not have UL resources, then the UEtriggers SR for the connectivity 1. It means that the UE sends SR onPUCCH or performs the Random Access procedure to/on the eNodeB which issubject to the connectivity 1. The BSR MAC CE includes information onlyabout buffer status of radio bearers in set A.

-   -   If data on radio bears in set B arrives,

The UE triggers the BSR for the connectivity 2. It means that the UEreports the BSR (i.e., BSR MAC CE) to the eNodeB which is subject to theconnectivity 2. Also, if the UE does not have UL resources, then the UEtriggers SR for the connectivity 2. It means that the UE sends SR onPUCCH or performs the Random Access procedure to/on the eNodeB which issubject to the connectivity 2. The BSR MAC CE includes information onlyabout buffer status of radio bearers in set B.

Also, BSR configurations including periodicBSR-Timer, retxBSR-Timer andso on can be configured per connectivity. In addition to BSRconfigurations, those timers operate on each connectivity.

eNodeB may want to know total amount of UE's data (in UL). In this case,eNodeB can order the UE to report the total amount of data in UL. Thisorder can be signaled by the PDCCH, MAC, RLC, PDCP, or RRC signaling.Also, eNodeB can configure the UE with periodic timer for reportingtotal amount of data in UL. The total amount of data can be indicated byamount of data per LCG, amount data per logical channel, amount of dataper connectivity or etc.

Also, the UE can report the amount of data for connectivity if theconnectivity is added, removed or modified. It means that the UEtriggers the BSR when the connectivity is added, removed or modified. Inthose cases, the UE sends the BSR to eNodeBs for which the configuredradio bears are changed. For example, the UE has two radio bears (A andB) for connectivity 1. If the UE is configured with a new connectivity 2and radio bearer B is configured for connectivity 2, then the UEtriggers the BSR for connectivity 2 and sends the BSR to the eNodeBwhich is subject to the connectivity 2, including the amount of data onradio bear B. Also, the UE triggers the BSR for connectivity 1 and sendsit to the eNodeB which is subject to the connectivity 1, including theamount of data on radio bears on radio bear A.

If the connectivity is removed, the UE triggers the BSR and sends it tothe CeNodeB (or other UeNodeBs) to indicate the amount of data for radiobears configured for the removed connectivity.

When the amount of data on radio bears configured for connectivity isindicated, the connectivity id can be indicated together to identify theconnectivity. For example, when the UE report BSR for connectivity 1,then the UE also indicates connectivity id assigned for connectivity 1along with the BSR.

<Logical Channel Prioritization (LCP)>

When the UE receives the UL grant from the eNodeB which is subject tocertain connectivity, during the LCP procedure, the data on radiobearers configured and/or control information for the connectivity isonly considered. For example, if the UE has 2 connectivity (A and B) andradio bearer “a” is configured for connectivity A and radio bearer “b”is configured for connectivity B, when the UE receives the UL grant fromthe eNodeB which is subject to the connectivity A, then the data onradio bearer “a” is considered for generating the MAC PDU by thereceived UL grant. I.e., in LCP procedure, the UL grant is onlyapplicable to the data on radio bearers configured for connectivity forwhich the UL grant is assigned.

<Power Headroom Reporting (PHR)>

The PHR configurations per connectivity can be provided to the UE. Also,PHR related timers can operate per connectivity.

If the UE triggers PHR, it sends the PHR MAC CE. The PHR MAC CE includesthe PH of cells belonging to the same connectivity.

When the connectivity is added, removed, or modified, the UE triggersthe PHR for one, some, or all the configured connectivity.

When the UE reports the PHs for connectivity, the UE can indicate theconnectivity Id.

<Maintenance of Uplink Timing Alignment>

Configuration about uplink timing alignment per connectivity can beprovided to the UE. Uplink timing alignment related timer (e.g.,timeAlignmentTimer) can operate per connectivity.

When the timeAlignmentTimer for connectivity for CeNodeB expires, the UEconsiders timeAlignmentTimer for all connectivity as expired.

When the Timing Advance Command is indicated, the connectivity Id isalso indicated. Then, the UE applies the Timing Advance Command for theconnectivity indicated by the connectivity Id and starts thetimeAlignmentTimer for the connectivity indicated by the connectivity Id

<Random Access Procedure>

The Random Access procedure is also performed per connectivity. If theRandom Access procedure needs to be performed at the same time on 2 ormore connectivity, the UE prioritizes the Random Access procedure on theconnectivity of the CeNodeB over connectivity of the UeNodeBs.

The ways or methods to solve the problem of the related art according tothe present disclosure, as described so far, can be implemented byhardware or software, or any combination thereof

FIG. 17 is a block diagram showing a wireless communication system toimplement an embodiment of the present invention.

An UE 100 includes a processor 101, memory 102, and a radio frequency(RF) unit 103. The memory 102 is connected to the processor 101 andconfigured to store various information used for the operations for theprocessor 101. The RF unit 103 is connected to the processor 101 andconfigured to send and/or receive a radio signal. The processor 101implements the proposed functions, processed, and/or methods. In thedescribed embodiments, the operation of the UE may be implemented by theprocessor 101.

The eNodeB (including CeNodeB and UeNodeB) 200/300 includes a processor201/301, memory 202/302, and an RF unit 203/303. The memory 202/302 isconnected to the processor 201/301 and configured to store variousinformation used for the operations for the processor 201/301. The RFunit 203/303 is connected to the processor 201/301 and configured tosend and/or receive a radio signal. The processor 201/301 implements theproposed functions, processed, and/or methods. In the describedembodiments, the operation of the eNodeB may be implemented by theprocessor 201.

The processor may include Application-Specific Integrated Circuits(ASICs), other chipsets, logic circuits, and/or data processors. Thememory may include Read-Only Memory (ROM), Random Access Memory (RAM),flash memory, memory cards, storage media and/or other storage devices.The RF unit may include a baseband circuit for processing a radiosignal. When the above-described embodiment is implemented in software,the above-described scheme may be implemented using a module (process orfunction) which performs the above function. The module may be stored inthe memory and executed by the processor. The memory may be disposed tothe processor internally or externally and connected to the processorusing a variety of well-known means.

In the above exemplary systems, although the methods have been describedon the basis of the flowcharts using a series of the steps or blocks,the present invention is not limited to the sequence of the steps, andsome of the steps may be performed at different sequences from theremaining steps or may be performed simultaneously with the remainingsteps. Furthermore, those skilled in the art will understand that thesteps shown in the flowcharts are not exclusive and may include othersteps or one or more steps of the flowcharts may be deleted withoutaffecting the scope of the present invention.

What is claimed is:
 1. A method for performing a logical channel prioritization, the method comprising: receiving an uplink (UL) grant; identifying a set of logical channels whose data are to be transmitted using the uplink grant; and performing a logical channel prioritization (LCP) based on the identified set of logical channels.
 2. The method of claim 1, wherein the performing the LCP is further based on: a control data to be transmitted using the uplink grant.
 3. The method of claim 1, further comprising: connecting with a first base station via a first MAC entity; and connecting with a second base station via a second MAC entity.
 4. The method of claim 3, wherein the performing of the LCP includes: if the first MAC entity receives the uplink grant, generating, by the first MAC entity, data unit based on the LCP; and transmitting, by the first MAC entity, the generated data unit to the first base station.
 5. The method of claim 4, wherein the generated data unit includes: data from the identified set of logical channels, except for a data from logical channels related to the second MAC entity and except for a control data related to the second MAC entity.
 6. The method of claim 3, wherein the performing of the LCP includes: if the second MAC entity receives the uplink grant, generating, by the second MAC entity, data unit based on the LCP; and transmitting, by the second MAC entity, the generated data unit to the second base station.
 7. The method of claim 6, wherein the generated data unit includes: data from the identified set of logical channels, except for a data from logical channels related to the first MAC entity and except for a control data related to the first MAC entity.
 8. A communication device configured for performing a logical channel prioritization, the communication device comprising: a radio frequency (RF) unit; and a processor connected with the RF unit thereby to control to: receive an uplink (UL) grant; identify a set of logical channels whose data are to be transmitted using the uplink grant; and perform a logical channel prioritization (LCP) based on the identified set of logical channels.
 9. The communication device of claim 8, wherein: the processor is configured to perform the LCP further based on a control data to be transmitted using the uplink grant.
 10. The communication device of claim 8, wherein the RF unit is configured to: connect with a first base station via a first MAC entity; and connect with a second base station via a second MAC entity.
 11. The communication device of claim 10, wherein: if the first MAC entity receives the uplink grant, the first MAC entity generates data unit based on the LCP and transmit the generated data unit to the first base station.
 12. The communication device of claim 11, wherein the generated data unit includes: data from the identified set of logical channels, except for a data from logical channels related to the second MAC entity and except for a control data related to the second MAC entity.
 13. The communication device of claim 10, wherein: if the second MAC entity receives the uplink grant, the second MAC entity generates data unit based on the LCP and transmits the generated data unit to the second base station.
 14. The communication device of claim 13, wherein the generated data unit includes: data from the identified set of logical channels, except for a data from logical channels related to the first MAC entity and except for a control data related to the first MAC entity. 